Catheters with enhanced flexibility and associated devices, systems, and methods

ABSTRACT

A neuromodulation catheter includes an elongate shaft and a neuromodulation element. The shaft includes two or more first cut shapes and two or more second cut shapes along a helical path extending around a longitudinal axis of the shaft. The first cut shapes are configured to at least partially resist deformation in response to longitudinal compression and tension on the shaft and torsion on the shaft in a first circumferential direction. The second cut shapes are configured to at least partially resist deformation in response to longitudinal compression on the shaft and torsion on the shaft in both first and second opposite circumferential directions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No. 15/227,691, filed Aug. 3, 2016, now U S Pat. No. 9,844,643, which is a Continuation of U.S. patent application Ser. No. 14/716,631, filed May 19, 2015, now U.S. Pat. No. 9,492,635, which is a Divisional of U.S. patent application Ser. No. 14/060,564, filed Oct. 22, 2013, now U.S. Pat. No. 9,044,575, which claims the benefit of the following applications:

(a) U.S. Provisional Application No. 61/717,067, filed Oct. 22, 2012;

(b) U.S. Provisional Application No. 61/793,144, filed Mar. 15, 2013; and

(c) U.S. Provisional Application No. 61/800,195, filed Mar. 15, 2013.

The foregoing applications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present technology is related to catheters. In particular, at least some embodiments are related to neuromodulation catheters having one or more cuts and/or other features that enhance flexibility, such as to facilitate intravascular delivery via transradial or other suitable percutaneous transluminal approaches.

BACKGROUND

The sympathetic nervous system (SNS) is a primarily involuntary bodily control system typically associated with stress responses. Fibers of the SNS extend through tissue in almost every organ system of the human body and can affect characteristics such as pupil diameter, gut motility, and urinary output. Such regulation can have adaptive utility in maintaining homeostasis or in preparing the body for rapid response to environmental factors. Chronic activation of the SNS, however, is a common maladaptive response that can drive the progression of many disease states. Excessive activation of the renal SNS in particular has been identified experimentally and in humans as a likely contributor to the complex pathophysiology of hypertension, states of volume overload (e.g., heart failure), and progressive renal disease.

Sympathetic nerves of the kidneys terminate in the renal blood vessels, the juxtaglomerular apparatus, and the renal tubules, among other structures. Stimulation of the renal sympathetic nerves can cause, for example, increased renin release, increased sodium reabsorption, and reduced renal blood flow. These and other neural-regulated components of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone. For example, reduced renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome, (i.e., renal dysfunction as a progressive complication of chronic heart failure). Pharmacologic strategies to thwart the consequences of renal sympathetic stimulation include centrally-acting sympatholytic drugs, beta blockers (e.g., to reduce renin release), angiotensin-converting enzyme inhibitors and receptor blockers (e.g., to block the action of angiotensin II and aldosterone activation consequent to renin release), and diuretics (e.g., to counter the renal sympathetic mediated sodium and water retention). These pharmacologic strategies, however, have significant limitations including limited efficacy, compliance issues, side effects, and others.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present technology. For ease of reference, throughout this disclosure identical reference numbers may be used to identify identical or at least generally similar or analogous components or features.

FIG. 1 is a partially schematic perspective view illustrating a therapeutic system including a neuromodulation catheter configured in accordance with an embodiment of the present technology.

FIG. 2 is an enlarged partially cut-away side view of a shaft of the neuromodulation catheter shown in FIG. 1 illustrating a hypotube of the shaft and a cut extending along a helical path having varying pitch along the length of the shaft.

FIG. 3 is a two-dimensional representation of the helical path shown in FIG. 2 and a portion of the shaft shown in FIG. 1.

FIG. 4 is a two-dimensional representation of the cut shown in FIG. 2 along a first portion of the helical path shown in FIG. 3.

FIG. 5 is a two-dimensional representation of the cut shown in FIG. 2 along a second portion of the helical path shown in FIG. 3.

FIGS. 6-9B are two-dimensional representations of cuts along portions of helical paths configured in accordance with embodiments of the present technology.

FIGS. 10-12 are perspective views of shaft segments having guide wire exit openings with different positions relative to cuts configured in accordance with embodiments of the present technology.

FIGS. 13 and 14 are perspective views of shaft segments including helically wound elongate members configured in accordance with embodiments of the present technology.

FIGS. 15 and 16 are side profile views of helically wound elongate members having windings with different average helix angles configured in accordance with embodiments of the present technology.

FIG. 17 is a side profile view of a helically wound elongate member having windings with different average helix angles on either side of a transition region configured in accordance with an embodiment of the present technology.

DETAILED DESCRIPTION

Neuromodulation catheters configured in accordance with at least some embodiments of the present technology include elongate shafts having one or more cuts and/or other features that enhance flexibility without unduly compromising desirable axial stiffness (e.g., pushability or other responsiveness to axial force) and/or desirable torsional stiffness (e.g., torqueability or other responsiveness to torsional force). For example, a neuromodulation catheter configured in accordance with a particular embodiment of the present technology is sufficiently flexible in some respects to facilitate deployment via a relatively long and/or tortuous intravascular path without excessive resistance, while still being sufficiently stiff in other respects so as to allow intravascular navigation or other suitable manipulation via an extracorporeal handle. Desirable axial stiffness can include, for example, the capability of the shaft to be advanced or withdrawn along the length of an intravascular path without significantly buckling or elongating. Desirable torsional stiffness can include, for example, the capability of the shaft to distally transfer rotational motion (e.g., from a handle at a proximal end portion of the shaft to a neuromodulation element operably connected to the shaft via a distal end portion of the shaft) with close correspondence (e.g., at least about one-to-one correspondence). In addition or alternatively, desirable torsional stiffness can include the capability of the shaft to distally transfer rotational motion without causing whipping and/or diametrical deformation of the shaft. Desirable axial and torsional stiffness together can facilitate predictable and controlled transmission of axial and torsional force from the proximal end portion of the shaft toward the distal end portion of the shaft while a neuromodulation catheter is in use.

Metal hypodermic (needle) tubing, aka hypotubing, is commonly incorporated into small-diameter shafts of medical catheters to utilize the wire-like physical properties of such material along with the useable lumen extending therethrough. However, solid-walled metal tubing also has known limitations regarding flexibility and kink resistance, and various designs have utilized slits, slots or other openings in the tubing wall to achieve improvements in flexibility. Such modifications to the wall structure have always brought about compromises in physical properties in tension, compression, and torsion. Thus, in at least some conventional neuromodulation catheters, imparting flexibility can require unduly sacrificing axial stiffness and/or torsional stiffness. For example, creating a continuous helical cut in a relatively rigid hypotube of a shaft tends to increase the flexibility of the shaft, but, in some instances, the resulting coils between turns of the cut may also tend to separate to an undesirable degree in response to tension on the shaft and/or torsion on the shaft in at least one circumferential direction. In some cases, this separation can cause a permanent or temporary change in the length of the shaft (e.g., undesirable elongation of the shaft), a permanent or temporary diametrical deformation of the shaft (e.g., undesirable flattening of a cross-section of the shaft), and/or torsional whipping. Such shaft behavior can interfere with intravascular navigation and/or have other undesirable effects on neuromodulation procedures.

Due, at least in part, to enhanced flexibility in combination with desirable axial and torsional stiffness, neuromodulation catheters configured in accordance with at least some embodiments of the present technology can be well-suited for intravascular delivery to treatment locations (e.g., treatment locations within or otherwise proximate to a renal artery of a human patient) via transradial approaches (e.g., approaches that include the radial artery, the subclavian artery, and the descending aorta). Transradial approaches are typically more tortuous and longer than femoral approaches and at least some other commonly used approaches. Transradial approaches can be desirable for accessing certain anatomy, but other types of approaches (e.g., femoral approaches) may be desirable in particularly tortuous anatomy or vessels having relatively small diameters. In some instances, however, use of transradial approaches can provide certain advantages over use of femoral approaches. In some cases, for example, use of transradial approaches can be associated with increased patient comfort, decreased bleeding, and/or faster sealing of the percutaneous puncture site relative to use of femoral approaches.

In addition to or instead of facilitating intravascular delivery via transradial approaches, neuromodulation catheters configured in accordance with at least some embodiments of the present technology can be well suited for intravascular delivery via one or more other suitable approaches, such as other suitable approaches that are shorter or longer than transradial approaches and other suitable approaches that are less tortuous or more tortuous than transradial approaches. For example, neuromodulation catheters configured in accordance with at least some embodiments of the present technology can be well suited for intravascular delivery via brachial approaches and/or femoral approaches. Even when used with approaches that are generally shorter and/or less tortuous than transradial approaches, the combination of flexibility and desirable axial and torsional stiffness associated with neuromodulation catheters configured in accordance with at least some embodiments of the present technology can be beneficial, such as to accommodate anatomical differences between patients and/or to reduce vessel trauma during delivery, among other potential benefits.

Specific details of several embodiments of the present technology are described herein with reference to FIGS. 1-17. Although many of the embodiments are described herein with respect to devices, systems, and methods for intravascular renal neuromodulation, other applications and other embodiments in addition to those described herein are within the scope of the present technology. For example, at least some embodiments may be useful for intraluminal neuromodulation, for extravascular neuromodulation, for non-renal neuromodulation, and/or for use in therapies other than neuromodulation. It should be noted that other embodiments in addition to those disclosed herein are within the scope of the present technology. For example, in still other embodiments, the technology described herein may be used in devices, systems and methods for stent delivery and balloon angioplasty. Further, embodiments of the present technology can have different configurations, components, and/or procedures than those shown or described herein. Moreover, a person of ordinary skill in the art will understand that embodiments of the present technology can have configurations, components, and/or procedures in addition to those shown or described herein and that these and other embodiments can be without several of the configurations, components, and/or procedures shown or described herein without deviating from the present technology.

As used herein, the terms “distal” and “proximal” define a position or direction with respect to a clinician or a clinician's control device (e.g., a handle of a neuromodulation catheter). The terms, “distal” and “distally” refer to a position distant from or in a direction away from a clinician or a clinician's control device. The terms “proximal” and “proximally” refer to a position near or in a direction toward a clinician or a clinician's control device. The headings provided herein are for convenience only and should not be construed as limiting the subject matter disclosed.

Selected Examples of Neuromodulation Catheters and Related Devices

FIG. 1 is a partially schematic perspective view illustrating a therapeutic system 100 configured in accordance with an embodiment of the present technology. The system 100 can include a neuromodulation catheter 102, a console 104, and a cable 106 extending therebetween. The neuromodulation catheter 102 can include an elongate shaft 108 having a proximal end portion 108 a and a distal end portion 108 b. A handle 110 of the neuromodulation catheter 102 can be operably connected to the shaft 108 via the proximal end portion 108 a, and a neuromodulation element 112 of the neuromodulation catheter 102 can be operably connected to the shaft 108 via the distal end portion 108 b. The shaft 108 can be configured to locate the neuromodulation element 112 intravascularly at a treatment location within or otherwise proximate to a body lumen (e.g., a blood vessel, a duct, an airway, or another naturally occurring lumen within the human body), and the neuromodulation element 112 can be configured to provide or support a neuromodulation treatment at the treatment location. The shaft 108 and the neuromodulation element 112 can be 2, 3, 4, 5, 6, or 7 French or one or more other suitable sizes.

In some embodiments, intravascular delivery of the neuromodulation catheter 102 includes percutaneously inserting a guide wire (not shown) into a body lumen of a patient and moving the shaft 108 and the neuromodulation element 112 along the guide wire until the neuromodulation element 112 reaches a suitable treatment location. In other embodiments, the neuromodulation catheter 102 can be a steerable or non-steerable device configured for use without a guide wire. In still other embodiments, the neuromodulation catheter 102 can be configured for delivery via a guide catheter or sheath (not shown).

The console 104 can be configured to control, monitor, supply, and/or otherwise support operation of the neuromodulation catheter 102. Alternatively, the neuromodulation catheter 102 can be self-contained or otherwise configured for operation without connection to the console 104. When present, the console 104 can be configured to generate a selected form and/or magnitude of energy for delivery to tissue at the treatment location via the neuromodulation element 112 (e.g., via one or more energy delivery elements (not shown) of the neuromodulation element 112). The console 104 can have different configurations depending on the treatment modality of the neuromodulation catheter 102. When the neuromodulation catheter 102 is configured for electrode-based, heat-element-based, or transducer-based treatment, for example, the console 104 can include an energy generator (not shown) configured to generate radio frequency (RF) energy (e.g., monopolar and/or bipolar RF energy), pulsed energy, microwave energy, optical energy, ultrasound energy (e.g., intravascularly delivered ultrasound, extracorporeal ultrasound, and/or high-intensity focused ultrasound (HIFU)), cryotherapeutic energy, direct heat energy, chemicals (e.g., drugs and/or other agents), radiation (e.g., infrared, visible, and/or gamma radiation), and/or another suitable type of energy. When the neuromodulation catheter 102 is configured for cryotherapeutic treatment, for example, the console 104 can include a refrigerant reservoir (not shown) and can be configured to supply the neuromodulation catheter 102 with refrigerant. Similarly, when the neuromodulation catheter 102 is configured for chemical-based treatment (e.g., drug infusion), the console 104 can include a chemical reservoir (not shown) and can be configured to supply the neuromodulation catheter 102 with one or more chemicals.

In some embodiments, the system 100 includes a control device 114 along the cable 106. The control device 114 can be configured to initiate, terminate, and/or adjust operation of one or more components of the neuromodulation catheter 102 directly and/or via the console 104. In other embodiments, the control device 114 can be absent or have another suitable location (e.g., within the handle 110). The console 104 can be configured to execute an automated control algorithm 116 and/or to receive control instructions from an operator. Furthermore, the console 104 can be configured to provide feedback to an operator before, during, and/or after a treatment procedure via an evaluation/feedback algorithm 118.

FIG. 2 is an enlarged partially cut-away side view of the shaft 108 illustrating a hypotube 120 concentrically disposed within an outside wall 121. The hypotube 120 can be configured to reinforce the shaft 108 against collapsing from lateral compression. For example, the hypotube 120 can be made of a relatively strong material (e.g., nitinol, stainless steel, or another suitable metal). The hypotube 120 may be disposed within all or a portion of the shaft 108. In some embodiments, for example, the hypotube 120 may only be disposed at a distal section of the shaft 108, and a proximal section of the shaft 108 may have a different arrangement and/or configuration. Tubes made of relatively strong materials tend to be relatively stiff (e.g., resistant to bending) when unmodified. To increase the flexibility of the neuromodulation catheter 102, the shaft 108 can include a cut 122 extending at least partially through a wall thickness of the hypotube 120, the outside wall 121, or another suitable portion of the shaft 108. For example, the shaft 108 can have a longitudinal axis 124 and the cut 122 can follow a helical path 126 that extends about the longitudinal axis 124 (e.g., a coiled, spiral, or other similar form having two or more turns consistently or variably spaced along the longitudinal axis 124). The cut 122 can be continuous or discontinuous along the helical path 126. Furthermore, the shaft 108 can be cut along more than one helical path 126 (e.g., a double helix having two or more helical paths 126 having the same “hand” or chirality and spaced apart along the longitudinal axis 124). The cut 122 can be formed, for example, using laser etching, electrical discharge machining, chemical etching, or other suitable techniques.

FIG. 3 is a two-dimensional representation of the helical path 126. In particular, FIG. 3 is a representation of the helical path 126 and a portion of the shaft 108 with the x-axis in FIG. 3 corresponding to the longitudinal axis 124 along at least a portion of the length of the shaft 108 and the y-axis in FIG. 3 corresponding to the circumference of the shaft 108. In other words, FIG. 3 illustrates the helical path 126 as though at least a portion of the shaft 108 were aligned with the x-axis and rolled along the y-axis with the helical path 126 unwinding to a flat ribbon or making an imprinted image as the shaft 108 is rolled. The helical path 126 can include a first portion 126 a, a second portion 126 b, and a third portion 126 c therebetween. The first portion 126 a, the second portion 126 b, and the third portion 126 c can extend around portions of the longitudinal axis 124 corresponding to a first segment 127 a, a second segment 127 b, and a third segment 127 c of the shaft 108, respectively. In some embodiments, the first segment 127 a is distal to the second and third segments 127 b, 127 c, and the third segment 127 c is between the first and second segments 127 a, 127 b. In other embodiments, the first, second, and third segments 127 a-c can be reversed or have another suitable arrangement. The first, second, and third segments 127 a-c can be directly adjacent to one another or spaced apart from one another along the longitudinal axis 124. Furthermore, the first segment 127 a can be directly adjacent to or spaced apart from a distalmost portion of the shaft 108 (e.g., a junction between the shaft 108 and the neuromodulation element 112), and the second segment 127 b can be directly adjacent to or spaced apart from a proximalmost portion of the shaft 108 (e.g., a junction between the shaft 108 and the handle 110).

As shown in FIG. 3, the first, second, and third portions 126 a-126 c of the helical path 126 can have different slopes when transposed two-dimensionally. These slopes can correspond to the axial density (e.g., frequency or pitch angle) of turns, shapes, or other suitable features of the cut 122 along the longitudinal axis 124. For example, the first portion 126 a of the helical path 126 can have a greater slope than the second portion 126 b, and the third portion 126 c can be curved with a slope that gradually transitions between the slopes of the first and second portions 126 a, 126 b. Accordingly, the cut 122 can have a greater axial density of turns, shapes, or other suitable features along a portion of the longitudinal axis 124 corresponding to the first segment 127 a than along a portion of the longitudinal axis 124 corresponding to the second segment 127 b. Similarly, the axial density of turns, shapes, or other suitable features of the cut 122 along the longitudinal axis 124 can increase gradually or in another suitable manner along the third segment 127 c from the second segment 127 b toward the first segment 127 a. For example, gradually increasing or otherwise transitioning the axial density of turns, shapes, slope, type, size/dimension, or other suitable features of the cut 122 may reduce focused stress on the shaft 108, which can reduce or eliminate kinking or other undesirable behavior of the shaft 108 when it bends.

By varying the axial density of turns, shapes, or other suitable features of the cut 122, different segments of the shaft 108 can have different levels of flexibility. For example, with reference to FIGS. 1-3 together, a greater axial density of turns, shapes, or other suitable features can correspond to greater flexibility than a lesser axial density of turns, shapes, or other suitable features. In some cases, a distance along the longitudinal axis 124 between the neuromodulation element 112 and a cut segment of the shaft 108 (e.g., the first, second, or third segment 127 a-c) can be selected such that the cut segment tends to be disposed in or near a particular anatomical location when the neuromodulation catheter 102 is in use. For example, the distance along the longitudinal axis 124 between the neuromodulation element 112 and the cut segment can be selected such that the cut segment tends to be at least proximate to a relatively sharply angled or otherwise relatively tortuous anatomic region of an approach (e.g., a transradial or other suitable approach) when the neuromodulation element 112 is at a selected treatment location (e.g., a treatment location within or otherwise proximate to a renal artery of a human patient). The relatively sharply angled or otherwise relatively tortuous region, for example, can be a region within or otherwise proximate to a subclavian artery (e.g., a portion of a subclavian artery adjacent to the descending aorta), an ostium of a renal artery, or another suitable anatomical feature. The axial density of turns, shapes, or other suitable features of the cut 122 along different segments of the shaft 108 and the relative flexibilities of the different segments can be selected to facilitate transradial catheterization or deployment of the neuromodulation catheter 102 via another suitable approach. In some embodiments, an axial density of turns, shapes, or other suitable features of the cut 122 along the longitudinal axis 124 varies along the length of the shaft 108 (e.g., to tailor the shaft 108 to the tortuosity or other geometry of different portions of a transradial or other suitable approach). In other embodiments, the axial density of turns, shapes, or other suitable features of the cut 122 along the longitudinal axis 124 can be consistent along the length of the shaft 108 (e.g., to increase the overall flexibility of the shaft 108).

FIG. 4 is a two-dimensional representation of the cut 122 along the first portion 126 a of the helical path 126. Such a two-dimensional representation is as if the shaft were rolled over a flat surface to leave an imprint of the cut shape therein. In some instances, these two dimensional representations can be used as input for an automated manufacturing process used to form cut shapes along a path in a tubular workpiece. With reference to FIGS. 2-4 together, the shaft 108 can include two or more first cut shapes 128 and two or more second cut shapes 130 interspersed along the helical path 126, with the first and second cut shapes 128, 130 forming portions of the cut 122. The first cut shapes 128 can be configured to at least partially interlock to thereby resist deformation in response to a set of three types of force acting on the shaft 108, and the second cut shapes 130 can be configured to at least partially interlock to thereby resist deformation in response to a different, complementary set of three types of force acting on the shaft 108. The sets can be different combinations of (a) compression along the longitudinal axis 124, (b) tension along the longitudinal axis 124, (c) torsion in a first circumferential direction perpendicular to the longitudinal axis 124, and (d) torsion in a second, opposite circumferential direction perpendicular to the longitudinal axis 124. For example, the first cut shapes 128 can be configured to at least partially resist deformation in response to compression on the shaft 108, tension on the shaft 108, and torsion on the shaft 108 in the first circumferential direction, and the second cut shapes 130 can be configured to at least partially resist deformation in response to compression on the shaft 108, torsion on the shaft 108 in the first circumferential direction, and torsion on the shaft 108 in a second circumferential direction opposite to the first circumferential direction. The first cut shapes 128 can be less resistant to deformation in response to torsion on the shaft 108 in the second circumferential direction than the second cut shapes 130. Similarly, the second cut shapes 130 can be less resistant to deformation in response to tension on the shaft 108 than the first cut shapes 128. Working together, the first and second cut shapes 128, 130 can provide the shaft 108 with sufficient resistance to deformation in response to all types of axial and torsional force that may act on the shaft 108 during use of the neuromodulation catheter 102.

In some embodiments, the first and second cut shapes 128, 130 are sinusoidal and have amplitudes with different (e.g., perpendicular) orientations relative to the longitudinal axis 124. In other embodiments, the first and second cut shapes 128, 130 can have other suitable forms. For example, as shown in FIG. 4, the first cut shapes 128 can individually include a first peak 132 (e.g., a first finger) and a second peak 134 (e.g., a second finger) with a first interface 136 therebetween. The first interface 136 can be perpendicular to the longitudinal axis 124 (FIG. 2). The second cut shapes 130 can individually include a third peak 138 (e.g., a third finger) and a fourth peak 140 (e.g., a fourth finger) with a second interface 142 therebetween. The second interface 142 can be parallel to the longitudinal axis 124. Alternatively, the first and second interfaces 136, 142 can have other suitable angles relative to the longitudinal axis 124, such as other suitable angles in which an angle between the first interface 136 and the longitudinal axis 124 is greater than an angle between the second interface 142 and the longitudinal axis 124. The first and second cut shapes 128, 130 can be configured to at least partially resist deformation in response to forces perpendicular to the first and second interfaces 136, 142, respectively. For example, such forces can cause the first and second peaks 132, 134 or the third and fourth peaks 138, 140 to at least partially interlock and thereby prevent or reduce widening of the cut 122.

FIG. 5 is a two-dimensional representation of the cut 122 along the second portion 126 b of the helical path 126. With reference to FIGS. 2, 3 and 5 together, an average length of the first interfaces 136, an average length of the second interfaces 142, or both can be different at different portions of the helical path 126. For example, the average length of the second interfaces 142 can be greater among the second cut shapes 130 along the second portion 126 b of the helical path 126 and the second segment 127 b of the shaft 108 than among the second cut shapes 130 along the first portion 126 a of the helical path 126 and the first segment 127 a of the shaft 108. In some cases, the average length of the first interfaces 136, the second interfaces 142, or both are selected based on different axial densities of turns, shapes, or other suitable features of the cut 122 at different segments of the shaft 108. For example, when the axial density is greater, the lengths of the first and second interfaces 136, 142 can be more restricted than when the axial density is lower (e.g., so as to avoid overlapping at adjacent turns).

FIGS. 6-9B are two-dimensional representations of cuts along portions of helical paths configured in accordance with further embodiments of the present technology. As shown in FIG. 6, for example, in some embodiments a shaft 108 includes an uncut region 144 with the first and second cut shapes 128, 130 positioned along portions of a helical path on either side of the uncut region 144. For example, the uncut region 144 can be one of many uncut regions 144 interspersed among the first and second cut shapes 128, 130 along the helical path. In other embodiments, the first and second cut shapes 128, 130 can be portions of a continuous cut. For example, as shown in FIG. 7, the first and second cut shapes 128, 130 can be in suitable patterns along the helical path other than one-to-one alternating patterns. Suitable patterns can include, for example, random patterns, non-random patterns, two-to-one alternating patterns, two-to-two alternating patterns, and three-to-two alternating patterns, among others. Furthermore, the spacing between adjacent first and second cut shapes 128, 130 can be consistent or variable.

Referring next to FIG. 8, a shaft can include two or more third cut shapes 146 and two or more fourth cut shapes 148 interspersed along a helical path. The individual third cut shapes 146 can be configured to fully interlock rather than partially interlock. For example, the individual third cut shapes 146 can be configured to at least partially resist deformation in response to compression on the shaft, tension on the shaft, torsion on the shaft in the first circumferential direction, and torsion on the shaft in the second circumferential direction. The shaft, for example, can include tabs 149 (e.g., protrusions, lobes, or other suitable structures) adjacent to the third cut shapes 146, with the third cut shapes 146 forming recesses complementary to the tabs 149. The individual tabs 149 can include a flared portion 149 a (e.g., a rounded head portion) and a restricted portion 149 b (e.g., a rounded neck portion), or other suitable structures. The fourth cut shapes 148 can be sinusoidal and have amplitudes oriented perpendicularly to the helical path. For example, the individual fourth cut shapes 148 can include a first peak 150 and a second peak 152 with an interface 154 therebetween that is diagonal relative to a longitudinal axis of the shaft and perpendicular to the helical path.

As shown in FIGS. 9A and 9B, in some embodiments a shaft includes the third cut shapes 146 without the fourth cut shapes 148. Referring to FIG. 9B, for example, the shaft includes tabs 302 adjacent to respective third cut shapes 300. The individual tabs 302 and corresponding third cut shapes 300, for example, can comprise a wedge-shaped arrangement with the tabs 302 including a wedge-shaped portion 304 (i.e., a “tail”) and a restricted neck portion 306, while the complementary third cut shapes 300 form recesses or sockets (i.e., “tail sockets”) complementary to the tabs 302. In some embodiments, the tabs 302 and third cut shapes 300 may fit snugly with very little room between the respective portions of the two components. In other embodiments, however, there may be some space between at least a portion of each wedge-shaped portion 304 and the complementary socket portion to allow some amount of relative movement between the components.

In other embodiments, the shaft can include the fourth cut shapes 148 without the third cut shapes 146. Although the third and fourth cut shapes 146, 148 are potentially useful alone or in combination with other cut shapes, it is expected that combinations of the first and second cut shapes 128, 130 may be more stable than the third and fourth cut shapes 146, 148 alone or in combination during use of a neuromodulation catheter. For example, is it expected that combinations of cut shapes that impart resistance to complementary sets of fewer than all types of axial and torsional force that may act on a shaft during use of a neuromodulation catheter may facilitate dissipation of localized stresses along a cut. It will further be appreciated that catheters configured in accordance with embodiments of the present technology can include various combinations of cut shapes tailored to provide a desired level of flexibility and/or control for different applications.

FIGS. 10-12 are perspective views of shaft segments having guide wire exit openings with different positions relative to cuts. For example, with reference to FIGS. 5 and 10, in some embodiments a shaft segment 156 having the first and second cut shapes 128, 130 has a guide wire exit opening 158 in place of a third peak 138 of one of the second cut shapes 130. In other embodiments, the guide wire exit opening 158 can be in place of the first peak 132, the second peak 134, the fourth peak 140, or a combination thereof including or not including the third peak 138. As another example, with reference to FIGS. 5 and 11, a shaft segment 160 having the first and second cut shapes 128, 130 can have a guide wire exit opening 162 between (e.g., about evenly between) adjacent turns of a helical path along which the first and second cut shapes 128, 130 are distributed. As yet another example, with reference to FIGS. 5, 6 and 12, a shaft segment 164 having the first and second cut shapes 128, 130 and the uncut region 146 (e.g., as described above with reference to FIG. 6) can have a guide wire exit opening 166 at the uncut region 146. In other examples, the guide wire exit openings may have other suitable positions relative to the cuts. Furthermore, although the guide wire exit openings 158, 162, 166 are illustrated in FIGS. 10-12 as generally oval with their longitudinal axes aligned with longitudinal axes of the corresponding shaft segments 156, 160, 164, the guide wire exit openings 158, 162, 166 can have other suitable shapes and/or orientations.

Instead of or in addition to a cut tube, neuromodulation catheters configured in accordance with at least some embodiments of the present technology can include one or more elongate members (e.g., filaments, wires, ribbons, or other suitable structures) helically wound into one or more tubular shapes. Similar to the axial density of turns, shapes, or other suitable features of a cut along a longitudinal axis of a shaft (e.g., as discussed above with reference to FIG. 3), the axial density of windings of a helically wound elongate member along a longitudinal axis of a shaft can be selected to change the flexibility of the shaft. For example, an axial density of windings along a longitudinal axis of a shaft can be selected to facilitate intravascular delivery of a neuromodulation element to a treatment location within or otherwise proximate to a renal artery of a human patient via a transradial or other suitable approach. In some embodiments, an axial density of windings along a longitudinal axis of a shaft varies along the length of the shaft (e.g., to tailor the shaft to the tortuosity or other geometry of different portions of a transradial or other suitable approach). In other embodiments, the axial density of windings along a longitudinal axis of a shaft can be consistent along the length of the shaft (e.g., to increase the overall flexibility of the shaft).

FIGS. 13 and 14 are perspective views of shaft segments including helically wound elongate members configured in accordance with embodiments of the present technology. With reference to FIG. 13, a shaft 168 can include a first helically wound elongate member 170 having a series of first windings 172 at least partially forming a first tubular structure 174. The shaft 168 can further include a second helically wound elongate member 176 having a series of second windings 178 at least partially forming a second tubular structure 180. The first tubular structure 174 can be disposed within the second tubular structure 180, and the first and second tubular structures 174, 180 can be concentric.

In some embodiments, at least one of the first and second helically wound elongate members 170, 176 is multifilar. For example, in the embodiment shown in FIG. 13, the second helically wound elongate member 176 is multifilar with five parallel filaments (individually identified in FIG. 13 as 176 a-e), and the first helically wound elongate member 170 is monofilar. In other embodiments, the second helically wound elongate member 176 can be monofilar and the first helically wound elongate member 170 can be multifilar. In still other embodiments, both the first and second helically wound elongate members 170, 176 can be monofilar or multifilar. Furthermore, in some embodiments, the first windings 172, the second windings 178, or both are “openly wound” or spaced apart along a longitudinal axis of the shaft 168. For example, in the embodiment shown in FIG. 13, the second windings 178 are shown spaced apart along the longitudinal axis of the shaft 168 with gaps 181 between adjacent second windings 178, and the first windings 172 are shown not spaced apart along the longitudinal axis of the shaft 168. In other embodiments, the second windings 178 can be not spaced apart along the longitudinal axis of the shaft 168 and the first windings 172 can be spaced apart along the longitudinal axis of the shaft 168. In still other embodiments, both the first and second windings 172, 178 can be spaced apart or not spaced apart along the longitudinal axis of the shaft 168.

With reference to FIG. 14, a shaft 182 can include a third helically wound elongate member 183 having a series of third windings 184 at least partially forming a third tubular structure 186. The first and second tubular structures 174, 180 can be disposed within the third tubular structure 186, and the first, second, and third tubular structures 174, 180, 186 can be concentric. In the embodiment shown in FIG. 14, the third helically wound elongate member 183 is multifilar with parallel filaments (individually identified in FIG. 14 as 183 a-e). In other embodiments, the third helically wound elongate member 183 can be monofilar. Furthermore, in embodiments having more than one helically wound layer, the layers may be counter-wound, e.g. a right-hand helical layer may surround a left-hand helical layer. The shaft 182 can further include biocompatible jacket 188 at least partially encasing the first, second, and third tubular structures 174, 180, 186. The biocompatible jacket 188, for example, can be at least partially made of a smooth polymer or other suitable material well suited for sliding contact with an inner wall of a body lumen.

FIG. 15 is a side profile view of a helically wound elongate member 190 having a series of windings 192 with an average helix angle A1. FIG. 16 is a side profile view of a helically wound elongate member 194 having a series of windings 196 with an average helix angle A2. With reference to FIGS. 14-16 together, the first windings 172, the second windings 178, the third windings 184, or a subset thereof, can have different average helix angles. For example, a first average helix angle of the first windings 172 can be different than a second average helix angle of the second windings 178 by an angle within a range from about 10 degrees to about 140 degrees (e.g., a range from about 30 degrees to about 120 degrees, or another suitable range). Similarly, the first average helix angle of the first windings 172 can be different than a third average helix angle of the third windings 184 by an angle within a range from about 10 degrees to about 140 degrees (e.g., a range from about 30 degrees to about 120 degrees, or another suitable range) and the second average helix angle of the second windings 178 can be between (e.g., about midway between) the first and third average helix angles of the first and third windings 172, 184, respectively.

FIG. 17 is a side profile view of a helically wound elongate member 198 having a series of windings 200 with different average helix angles and opposite chirality on either side of a transition region 202. Although an abrupt change in average helix angle at the transition region 202 is shown in FIG. 17, the change at the transition region 202 can alternatively be gradual or incremental. With reference to FIGS. 14, 15 and 17 together, in some embodiments the first windings 172, the second windings 178, and/or the third windings 184 include one or more transition regions 202. In other embodiments, the first windings 172, the second windings 178, and the third windings 184 can have consistent helix angles along the length of the shaft 168. Including one or more transition regions 202 can be useful, for example, to allow a difference between average helix angles of windings within concentric tubular structures to vary (e.g., to change at least once) along the length of the shaft 168. For example, this difference can decrease (e.g., abruptly, gradually, or incrementally) distally along the length of the shaft 168. It is expected that increasing a difference between average helix angles of windings within concentric tubular structures may reduce flexibility and increase axial and torsional stiffness of a shaft, and that decreasing a difference between average helix angles of windings within concentric tubular structures may increase flexibility and decrease axial and torsional stiffness of a shaft. Accordingly, the positions of the transition regions 202 can be selected to change the flexibility of the shaft relative to the axial and torsional stiffness of the shaft along the length of a shaft (e.g., to facilitate intravascular delivery of a neuromodulation element to a treatment location within or otherwise proximate to a renal artery of a human patient via a transradial or other suitable approach).

Instead of or in addition to a cut tube and/or a helically wound elongate member, neuromodulation catheters configured in accordance with at least some embodiments of the present technology can include shafts having one or more segments with different shape memory properties. With reference to FIG. 3, for example, the first segment 127 a can be made at least partially of a first shape-memory alloy, the second segment 127 b can be made at least partially of a second shape-memory alloy, and the third segment 127 c can be made at least partially of a third shape-memory alloy. The first, second, and third shape-memory alloys can be different or the same. In some embodiments, the first, second, and third shape-memory alloys are nitinol. In other embodiments, the first, second, and third shape-memory alloys can be other suitable materials. The first, second, and third shape-memory alloys can have first, second, and third shape-memory transformation temperature ranges, respectively. For example, when the first, second, and third shape-memory alloys are nitinol, the first, second, and third shape-memory transformation temperature ranges can include Af temperatures.

The second shape-memory transformation temperature range and/or an Af temperature of the second shape-memory transformation temperature range can be lower than the first shape-memory transformation temperature range and/or an Af temperature of the first shape-memory transformation temperature range. For example, the first shape-memory transformation temperature range can include an Af temperature greater than body temperature and the second shape-memory transformation temperature range includes an Af temperature less than body temperature. A shape-memory transformation temperature range and/or an Af temperature of a shape-memory transformation temperature range of the shaft 108 can increase (e.g., abruptly, gradually, or incrementally) along the third segment 127 c from the second segment 127 b toward the first segment 127 a. In some embodiments, to vary the shape-memory transformation temperature ranges and/or Af temperatures along the length of the shaft 108, the first, second, and third segments 127 a-c are formed separately and then joined. In other embodiments, the shape-memory transformation temperature ranges and/or the Af temperatures along the length of the shaft 108 can be achieved by processing the first, second, and third segments 127 a-c differently while they are joined. For example, one of the first, second, and third segments 127 a-c can be subjected to a heat treatment to change its shape-memory transformation temperature range and/or Af temperature while the others of the first, second, and third segments 127 a-c are thermally insulated.

It is expected that greater shape-memory transformation temperature ranges and/or Af temperatures of shape-memory transformation temperature ranges may increase flexibility and decrease axial and torsional stiffness of a shaft (e.g., by causing nitinol to tend to assume a austenite phase at body temperature), and that lower shape-memory transformation temperature ranges and/or Af temperatures of shape-memory transformation temperature ranges may decrease flexibility and increase axial and torsional stiffness of a shaft (e.g., by causing nitinol to tend to assume a martensite phase at body temperature). Accordingly, the positions of segments of a shaft having different shape-memory transformation temperature ranges and/or Af temperatures of shape-memory transformation temperature ranges can be selected to change the flexibility of the shaft relative to the axial and torsional stiffness of the shaft along the length of a shaft (e.g., to facilitate intravascular delivery of a neuromodulation element to a treatment location within or otherwise proximate to a renal artery of a human patient via a transradial or other suitable approach).

Renal Neuromodulation

Renal neuromodulation is the partial or complete incapacitation or other effective disruption of nerves of the kidneys (e.g., nerves terminating in the kidneys or in structures closely associated with the kidneys). In particular, renal neuromodulation can include inhibiting, reducing, and/or blocking neural communication along neural fibers (e.g., efferent and/or afferent neural fibers) of the kidneys. Such incapacitation can be long-term (e.g., permanent or for periods of months, years, or decades) or short-term (e.g., for periods of minutes, hours, days, or weeks). Renal neuromodulation is expected to contribute to the systemic reduction of sympathetic tone or drive and/or to benefit at least some specific organs and/or other bodily structures innervated by sympathetic nerves. Accordingly, renal neuromodulation is expected to be useful in treating clinical conditions associated with systemic sympathetic overactivity or hyperactivity, particularly conditions associated with central sympathetic overstimulation. For example, renal neuromodulation is expected to efficaciously treat hypertension, heart failure, acute myocardial infarction, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic and end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, polycystic kidney disease, polycystic ovary syndrome, osteoporosis, erectile dysfunction, and sudden death, among other conditions.

Renal neuromodulation can be electrically-induced, thermally-induced, chemically-induced, or induced in another suitable manner or combination of manners at one or more suitable treatment locations during a treatment procedure. The treatment location can be within or otherwise proximate to a renal lumen (e.g., a renal artery, a ureter, a renal pelvis, a major renal calyx, a minor renal calyx, or another suitable structure), and the treated tissue can include tissue at least proximate to a wall of the renal lumen. For example, with regard to a renal artery, a treatment procedure can include modulating nerves in the renal plexus, which lay intimately within or adjacent to the adventitia of the renal artery.

Renal neuromodulation can include a cryotherapeutic treatment modality alone or in combination with another treatment modality. Cryotherapeutic treatment can include cooling tissue at a treatment location in a manner that modulates neural function. For example, sufficiently cooling at least a portion of a sympathetic renal nerve can slow or potentially block conduction of neural signals to produce a prolonged or permanent reduction in renal sympathetic activity. This effect can occur as a result of cryotherapeutic tissue damage, which can include, for example, direct cell injury (e.g., necrosis), vascular or luminal injury (e.g., starving cells from nutrients by damaging supplying blood vessels), and/or sublethal hypothermia with subsequent apoptosis. Exposure to cryotherapeutic cooling can cause acute cell death (e.g., immediately after exposure) and/or delayed cell death (e.g., during tissue thawing and subsequent hyperperfusion). Neuromodulation using a cryotherapeutic treatment in accordance with embodiments of the present technology can include cooling a structure proximate an inner surface of a body lumen wall such that tissue is effectively cooled to a depth where sympathetic renal nerves reside. For example, in some embodiments, a cooling assembly of a cryotherapeutic device can be cooled to the extent that it causes therapeutically-effective, cryogenic renal neuromodulation. In other embodiments, a cryotherapeutic treatment modality can include cooling that is not configured to cause neuromodulation. For example, the cooling can be at or above cryogenic temperatures and can be used to control neuromodulation via another treatment modality (e.g., to protect tissue from neuromodulating energy).

Renal neuromodulation can include an electrode-based or transducer-based treatment modality alone or in combination with another treatment modality. Electrode-based or transducer-based treatment can include delivering electricity and/or another form of energy to tissue at a treatment location to stimulate and/or heat the tissue in a manner that modulates neural function. For example, sufficiently stimulating and/or heating at least a portion of a sympathetic renal nerve can slow or potentially block conduction of neural signals to produce a prolonged or permanent reduction in renal sympathetic activity. A variety of suitable types of energy can be used to stimulate and/or heat tissue at a treatment location. For example, neuromodulation in accordance with embodiments of the present technology can include delivering RF energy, pulsed energy, microwave energy, optical energy, focused ultrasound energy (e.g., high-intensity focused ultrasound energy), or another suitable type of energy alone or in combination. An electrode or transducer used to deliver this energy can be used alone or with other electrodes or transducers in a multi-electrode or multi-transducer array. Furthermore, the energy can be applied from within the body (e.g., within the vasculature or other body lumens in a catheter-based approach) and/or from outside the body (e.g., via an applicator positioned outside the body). Furthermore, energy can be used to reduce damage to non-targeted tissue when targeted tissue adjacent to the non-targeted tissue is subjected to neuromodulating cooling.

Neuromodulation using focused ultrasound energy (e.g., high-intensity focused ultrasound energy) can be beneficial relative to neuromodulation using other treatment modalities. Focused ultrasound is an example of a transducer-based treatment modality that can be delivered from outside the body. Focused ultrasound treatment can be performed in close association with imaging (e.g., magnetic resonance, computed tomography, fluoroscopy, ultrasound (e.g., intravascular or intraluminal), optical coherence tomography, or another suitable imaging modality). For example, imaging can be used to identify an anatomical position of a treatment location (e.g., as a set of coordinates relative to a reference point). The coordinates can then entered into a focused ultrasound device configured to change the power, angle, phase, or other suitable parameters to generate an ultrasound focal zone at the location corresponding to the coordinates. The focal zone can be small enough to localize therapeutically-effective heating at the treatment location while partially or fully avoiding potentially harmful disruption of nearby structures. To generate the focal zone, the ultrasound device can be configured to pass ultrasound energy through a lens, and/or the ultrasound energy can be generated by a curved transducer or by multiple transducers in a phased array (curved or straight).

Heating effects of electrode-based or transducer-based treatment can include ablation and/or non-ablative alteration or damage (e.g., via sustained heating and/or resistive heating). For example, a treatment procedure can include raising the temperature of target neural fibers to a target temperature above a first threshold to achieve non-ablative alteration, or above a second, higher threshold to achieve ablation. The target temperature can be higher than about body temperature (e.g., about 37° C.) but less than about 45° C. for non-ablative alteration, and the target temperature can be higher than about 45° C. for ablation. Heating tissue to a temperature between about body temperature and about 45° C. can induce non-ablative alteration, for example, via moderate heating of target neural fibers or of vascular or luminal structures that perfuse the target neural fibers. In cases where vascular structures are affected, the target neural fibers can be denied perfusion resulting in necrosis of the neural tissue. Heating tissue to a target temperature higher than about 45° C. (e.g., higher than about 60° C.) can induce ablation, for example, via substantial heating of target neural fibers or of vascular or luminal structures that perfuse the target fibers. In some patients, it can be desirable to heat tissue to temperatures that are sufficient to ablate the target neural fibers or the vascular or luminal structures, but that are less than about 90° C. (e.g., less than about 85° C., less than about 80° C., or less than about 75° C.).

Renal neuromodulation can include a chemical-based treatment modality alone or in combination with another treatment modality. Neuromodulation using chemical-based treatment can include delivering one or more chemicals (e.g., drugs or other agents) to tissue at a treatment location in a manner that modulates neural function. The chemical, for example, can be selected to affect the treatment location generally or to selectively affect some structures at the treatment location over other structures. The chemical, for example, can be guanethidine, ethanol, phenol, a neurotoxin, or another suitable agent selected to alter, damage, or disrupt nerves. A variety of suitable techniques can be used to deliver chemicals to tissue at a treatment location. For example, chemicals can be delivered via one or more needles originating outside the body or within the vasculature or other body lumens. In an intravascular example, a catheter can be used to intravascularly position a therapeutic element including a plurality of needles (e.g., micro-needles) that can be retracted or otherwise blocked prior to deployment. In other embodiments, a chemical can be introduced into tissue at a treatment location via simple diffusion through a body lumen wall, electrophoresis, or another suitable mechanism. Similar techniques can be used to introduce chemicals that are not configured to cause neuromodulation, but rather to facilitate neuromodulation via another treatment modality.

Returning to FIG. 1, in another embodiment the system 100 may comprise a stent delivery system. In this embodiment, stent delivery catheter 102 includes stent delivery element 112. In one embodiment, stent delivery element 112 includes a dilatation balloon with a balloon expandable stent disposed thereon. The stent delivery catheter 102 also includes handle 110 operably connected to shaft 108 via proximal end portion 108 a. The shaft 108 can be configured to locate the stent delivery element 112 intravascularly at a treatment location within or otherwise proximate to a body lumen (e.g., coronary artery). The handle 110 is configured to aid in the delivery and deployment of the stent (not shown) to the treatment location. The stent delivery system 100 does not include the console 104 or cable 106.

The stent of stent delivery element 112 may be any balloon expandable stent as known to one of ordinary skill in the art. In one embodiment, for example, the stent is formed from a single wire forming a continuous sinusoid. The stent may include a coating disposed on the surface of the stent. The coating may include a polymer and/or a therapeutic agent. In one embodiment, the coating includes a Biolinx™ polymer blended with a limus drug. In another embodiment, the stent is a drug filled stent having a lumen filled with a therapeutic agent. In still another embodiment, element 112 does not include a stent disposed on the dilatation balloon.

Conclusion

This disclosure is not intended to be exhaustive or to limit the present technology to the precise forms disclosed herein. Although specific embodiments are disclosed herein for illustrative purposes, various equivalent modifications are possible without deviating from the present technology, as those of ordinary skill in the relevant art will recognize. In some cases, well-known structures and functions have not been shown and/or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Although steps of methods may be presented herein in a particular order, in alternative embodiments the steps may have another suitable order. Similarly, certain aspects of the present technology disclosed in the context of particular embodiments can be combined or eliminated in other embodiments. Furthermore, while advantages associated with certain embodiments may have been disclosed in the context of those embodiments, other embodiments can also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages or other advantages disclosed herein to fall within the scope of the present technology. Accordingly, this disclosure and associated technology can encompass other embodiments not expressly shown and/or described herein.

Throughout this disclosure, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Similarly, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the terms “comprising” and the like are used throughout this disclosure to mean including at least the recited feature(s) such that any greater number of the same feature(s) and/or one or more additional types of features are not precluded. Directional terms, such as “upper,” “lower,” “front,” “back,” “vertical,” and “horizontal,” may be used herein to express and clarify the relationship between various elements. It should be understood that such terms do not denote absolute orientation. Reference herein to “one embodiment,” “an embodiment,” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. Furthermore, various particular features, structures, operations, or characteristics may be combined in any suitable manner in one or more embodiments. 

We claim:
 1. A method for treating a human patient, the method comprising: advancing a neuromodulation element of a neuromodulation catheter along a transradial approach to a target site within a renal artery of the patient, wherein the neuromodulation element is at a distal end portion of a shaft of the neuromodulation catheter, and wherein the shaft includes two or more first cut shapes and two or more second cut shapes interspersed along a helical path extending about a longitudinal axis of the shaft; applying torsion to the shaft about the longitudinal axis while advancing the neuromodulation element, wherein the first cut shapes, to a greater extent than the second cut shapes, resist deformation of the shaft in response to the torsion; operating the neuromodulation element to modulate one or more nerves proximate a wall of the renal artery; withdrawing the neuromodulation element along the transradial approach after operating the neuromodulation element; and applying tension to the shaft along the longitudinal axis while withdrawing the neuromodulation element, wherein the second cut shapes, to a greater extent than the first cut shapes, resist deformation of the shaft in response to the tension.
 2. The method of claim 1 wherein applying torsion to the shaft includes distally transferring rotational motion from an extracorporeal handle of the neuromodulation catheter to the neuromodulation element via the shaft.
 3. The method of claim 1, further comprising interlocking the first cut shapes in response to the torsion.
 4. The method of claim 3, further comprising interlocking the second cut shapes in response to the tension.
 5. The method of claim 1 wherein: the first and second cut shapes are portions of a continuous cut; the first cut shapes, to a greater extent than the second cut shapes, resist deformation of the shaft at the continuous cut in response to the torsion; and the second cut shapes, to a greater extent than the first cut shapes, resist deformation of the shaft at the continuous cut in response to the tension.
 6. The method of claim 1 wherein the first cut shapes, to a greater extent than the second cut shapes, resist diametrical deformation of the shaft in response to the torsion.
 7. The method of claim 6 wherein the second cut shapes, to a greater extent than the first cut shapes, resist elongation of the shaft in response to the tension.
 8. The method of claim 1, further comprising locating the first and second cut shapes at a sharply angled portion of the transradial approach when the neuromodulation element is operably positioned within the renal artery.
 9. The method of claim 1, further comprising locating the first and second cut shapes within a subclavian artery of the patient when the neuromodulation element is operably positioned at the target site within the renal artery.
 10. The method of claim 1 wherein: the torsion is torsion in a second circumferential direction; the method further comprises applying torsion to the shaft about the longitudinal axis in a first circumferential direction opposite to the second circumferential direction while advancing the neuromodulation element; and the first and second cut shapes resist deformation of the shaft in response to the torsion in the first circumferential direction.
 11. The method of claim 1 wherein: the shaft includes two or more third cut shapes interspersed with the first and second cut shapes along the helical path; the third cut shapes, to a greater extent than the first cut shapes, resist deformation of the shaft in response to the tension; and the third cut shapes, to a greater extent than the second cut shapes, resist deformation of the shaft in response to the torsion.
 12. The method of claim 1 wherein operating the neuromodulation element to modulate the one or more nerves includes operating an electrode of the neuromodulation element to modulate the one or more nerves.
 13. The method of claim 1, further comprising advancing the shaft over a guidewire that exits the shaft via an exit opening at one of the second cut shapes.
 14. The method of claim 1, further comprising advancing the shaft over a guidewire that exits the shaft via an exit opening spaced apart from the helical path.
 15. A method for treating a human patient, the method comprising: intravascularly advancing a neuromodulation element of a neuromodulation catheter along a transradial approach to a renal artery of the patient, wherein the neuromodulation element is at a distal end portion of a shaft of the neuromodulation catheter, and wherein the shaft includes a tubular wall, a first hypotube segment concentrically disposed within the tubular wall, the first hypotube segment being made at least partially of a first shape-memory alloy having a first shape-memory transformation temperature range, and a second hypotube segment concentrically disposed within the tubular wall proximal to the first hypotube segment along a longitudinal axis of the shaft, the second hypotube segment being made at least partially of a second shape-memory alloy having a second shape-memory transformation temperature range lower than the first shape-memory transformation temperature range; and operating the neuromodulation element to modulate one or more nerves proximate a wall of the renal artery.
 16. The method of claim 15, further comprising distally transferring rotational motion from a handle of the neuromodulation catheter to the neuromodulation element via the shaft.
 17. The method of claim 15 wherein: the first shape-memory alloy is nitinol; and the method further comprises causing the nitinol of the first hypotube segment to assume an austenite phase while advancing the neuromodulation element.
 18. The method of claim 17 wherein: the second shape-memory alloy is nitinol; and the method further comprises causing the nitinol of the second hypotube segment to assume a martensite phase while advancing the neuromodulation element.
 19. The method of claim 17 wherein operating the neuromodulation element to modulate the one or more nerves includes operating an electrode of the neuromodulation element to modulate the one or more nerves.
 20. The method of claim 15, further comprising withdrawing the neuromodulation element along the transradial approach after operating the neuromodulation element. 